The connection of the timed-bar driver with the drive element has heretofore, as a rule, been by screws. After lengthy operation it is not possible to rule out the danger that such a connection may become loose, so that if this remains unobserved the timed-bar driver may become detached from the drive element. Because of the high transfer speed obtainable with this indexing drive, that would mean that the loosened timed-bar driver would be flung away with relatively great force, which would endanger the entire transfer line and its personnel.